The geometry dependence of several potential criteria for the onset of ductile fracture in tension tests was investigated for a modern tremethylcyclopentanone (TMCP) line pipe steel using an experimental/numerical approach. Large-strain finite-element simulations were used to estimate the state of stress and strain in highly instrumented notched and smooth tension tests of various geometries. The softening effect of void growth became significant only after the specimens had undergone extensive necking and had lost most of their load-carrying capacity. Therefore, for this steel, a practical fracture criterion can be based on the conditions at the onset of significant void growth, eliminating the need for void-growth modeling. At the onset of significant void growth, the maximum principal strain, the effective strain, and the strain energy density were independent of the tension-test geometry.